How to Choose a Double Glazing Company in Leicester: 7 Checks Before You Sign

The seven checks below take about an evening, and every one of them can be verified on an official website rather than taken on trust.

Why does it matter which double glazing company you choose?

It matters because replacement windows and doors are controlled building work, and the paperwork stays with your house long after the fitters have gone. The Planning Portal confirms that Building Regulations have applied to all replacement glazing since 1 April 2002, and GOV.UK lists replacing windows and doors among the jobs that need Building Regulations approval.

GOV.UK also sets out what happens when the work is not approved: the person doing the work can be prosecuted and fined, you can be made to pay for faulty work to be put right, and you will not have the compliance certificates you may need when you come to sell.

So the choice is about more than the frames. A good installer handles the approval for you. A poor one leaves you to sort it out with the council afterwards.

Check 1: Is the installer registered with FENSA or CERTASS?

Yes or no — this is the first thing to establish, and you can check it yourself in two minutes. An installer registered with a competent person scheme can self-certify that the work meets Building Regulations and notify the local authority for you, so you do not have to apply to building control yourself.

For replacement windows, doors, roof windows and rooflights in existing homes, the government’s list of authorised schemes names Blue Flame Certification, CERTASS, Certsure, FENSA, NAPIT and ASSURE. FENSA and CERTASS are the two you will hear most often from window companies.

How to check

• Ask the company for its registration number, in writing, before the survey.
• Search it on the scheme’s own website. FENSA’s installer search lets you look up a company by postcode, company name or FENSA ID number.
• If the name on the register does not match the name on your quote, ask why before you go any further.

Check 2: What should a FENSA certificate actually give you?

A FENSA certificate is the installer’s declaration to you that the windows and doors they replaced comply with Building Regulations, and that the job has been registered with the local council. FENSA also describes it as essential when you sell the property, and says it confirms the installer’s guarantee is insured.

Three details are worth knowing before you sign anything:

• Timing. GOV.UK says you should receive your certificate within 8 weeks of the work being completed. Put a note in your diary and chase it if it does not arrive.
• What it does not cover. FENSA lists conservatories, porches, new builds, extensions, repairs and commercial properties as outside the scheme. For those jobs, ask the installer how Building Regulations sign-off will be handled instead.
• If it goes missing. FENSA charges £30 including VAT for a replacement certificate ordered online. If there never was a certificate, FENSA warns you may have to pay for a building control inspection, and possibly for another installer to correct anything that does not comply.

Check 3: Does the quote show the energy rating the regulations ask for?

It should — and if it does not, ask for it in writing. Approved Document L sets the minimum thermal standard for replacement windows and doors in existing homes in England, and the figures are short enough to check against any quote.

Source: Approved Document L, Volume 1: Dwellings (2021 edition incorporating 2023 amendments), Table 4.2 and paragraph 10.3.

A lower U-value means less heat escaping. The letter rating is a different way of showing performance: the British Fenestration Rating Council (BFRC) rates windows and doors from A++ down to E, using three things together — heat loss, solar gain and air leakage.

Two practical tips

• A genuine BFRC-rated product carries a small official sticker on the inside of the frame. Only registered companies may use BFRC rating materials, and you can check a company on the BFRC Consumer Search.
• “A-rated” on a leaflet can refer to the glass, the frame or the whole window. Ask which one, and ask for the whole-window rating or U-value to be written on the quote.

Check 4: Will the new windows keep safety glass, ventilation and fire escape right?

They must — and this is the check most buying guides skip. Building Regulations for replacement windows cover more than heat loss. The Planning Portal lists safety glazing, ventilation and means of escape as part of the same rules, and they are the areas where a rushed survey goes wrong.

Source: Planning Portal, Doors and windows: Building Regulations.

Check 5: Is the guarantee insurance-backed, and is your deposit protected?

Both should be, and you should see it in writing before you pay anything. A guarantee is only as good as the company behind it, so the question to ask is what happens to it if that company closes.

GOV.UK notes that competent person schemes include insurance-backed warranties and complaints procedures, and FENSA says its certificate confirms the installer’s guarantee is insured. That still leaves your deposit, which is a separate risk between the day you order and the day the job is finished.

Ask each company

• Is the guarantee insurance-backed, and who is the insurer?
• Will I receive the policy document in my own name?
• Is my deposit protected from the day I pay it, and by which scheme?
• If we disagree about something, is there an independent route to resolve it?

Check 6: Is the price a single written figure, and what does it include?

A trustworthy quote is one written price, given after a survey, that says exactly what is included. The question Leicester homeowners ask us most is some version of “what’s your best price?”, and it is a fair question. The trouble is that two quotes are rarely for the same thing, so the cheaper figure is not always the cheaper job.

Before you compare totals, check that each quote covers the same list:

Be cautious of a figure that drops sharply if you agree to sign that evening. A fair price for your house today will still be a fair price next week.

Our own approach is simple. We survey for free, measure every opening properly, and give you one clear written price that covers the products, the fitting, the finishing and taking the old frames away. There is no pressure to sign on the day.

Check 7: Have they done your type of job before, locally?

Ask for proof, because experience with your kind of property matters more than the size of the company. “Have you done this before?” is one of the three questions our customers ask most, alongside price and FENSA, and it is the right instinct.

Leicester has a real mix of housing, from Victorian terraces in Clarendon Park to newer estates, and the jobs are not the same. A bay window has to be surveyed and templated individually. A period house may suit sliding sash or flush casement windows better than a standard casement. Turning a window into French doors is a different job again — one of our Google reviewers describes exactly that kind of conversion.

Things to look for

• Recent reviews that mention the type of work you want, not only star ratings.
• Photos of finished local jobs, and a straight answer about who fitted them.
• The names of the people you will deal with. If the person who sells is not the person who surveys or fits, ask how the details get passed on.

Big national brand or local firm?

We hear this often, and some people choose the bigger name because it feels safer. Our honest view is that size is not the test. FENSA assesses every approved installer regularly, from large national brands to small local companies, so both can pass or fail the seven checks in this guide. Run the same checks on everyone, us included.

At URG you deal with the same small team from the first survey to the day the job is finished. You can see who we are on our About Us page.

The 7 checks at a glance

Frequently asked questions

Do I need a FENSA certificate to sell my house?

You need evidence that replacement windows and doors comply with Building Regulations, and a FENSA certificate is the usual way to show it. GOV.UK says that without approval you will not have the compliance certificates you may need when you sell, and that a competent person scheme certificate shows up in solicitors’ searches. A certificate from another authorised scheme such as CERTASS, or from local authority building control, does the same job.

Is CERTASS as good as FENSA?

Both are on the government’s list of authorised competent person schemes for replacement windows, doors, roof windows and rooflights in existing homes. What matters is that the installer is currently registered with one of them and that the certificate is included in your quote.

How long after installation should my certificate arrive?

GOV.UK says within 8 weeks of the work being completed. If it has not arrived by then, contact the installer first and then the scheme they are registered with.

Does FENSA cover a new conservatory or porch?

No. FENSA lists conservatories, porches, new builds and extensions as outside its scheme, along with repairs and commercial properties. Ask your installer how Building Regulations compliance will be dealt with for that part of the job.

How long does it take to replace the windows in a whole house?

For a typical three-bedroom semi, most of our full-house installations are done in one to two days. We fit room by room so your home is never left open, and we clear up and take the old frames away with us.